An electrophotographic light-sensitive material (zinc oxide light-sensitive plate) comprising a conductive support having a photoconductive layer composed of zinc oxide and a resin binder formed directly or through an interlayer having an electric resistance to some extent on the support has been frequently used. The conductive support used in the foregoing case may be a metal plate, a paper subjected to a conductive treatment, NESA glass (conductive transparent glass), an aluminum-vapor deposited plastic sheet or an aluminum laminated paper. However, when using an electrophotographic light-sensitive material using zinc oxide for a lithographic printing plate having high printing resistance, a conductivity-imparted paper both surfaces of which are laminated by polyethylene containing 5 to 25% carbon at a thickness of 10 to 45 .mu.m is preferred in view of cost, easiness of handling and dimensional stability of the support during printing.
The photoconductive layer may be a layer of a dispersion of fine powder of zinc oxide in a resin binder such as shellac, paraffin, a vinyl resin, an acryl resin, a silicone resin, a phenol resin. Also, as the interlayer, a layer of polyvinyl alcohol, casein, carboxyl methyl cellulose, gum arabic, polyamide, polyester, etc. is employed.
For an electrophotographic lithographic printing material, a conductivity-imparted paper is most generally used as the support thereof but when using such a support, the printing durability is usually 2,000 to 3,000 prints and also the support extends 1 to 2% of the original length by the action of a fountain or dampening solution used for lithographic printing. Accordingly, the development of electrophotographic lithographic light-sensitive materials which have a high printing durability of 10,000 to 20,000 prints with good accuracy and are prepared at a cost not so much higher than that of conventional light-sensitive materials has been desired.
The inventors previously proposed a support composed of a conductivity-imparted paper having laminated on both surfaces thereof, polyethylene containing a conductivity-imparting agent such as carbon, etc., as shown in Japanese Patent Application 156829/81 (U.S. application Ser. No. 427,037). The support works well. However, under some conditions, the photoconductive layer partially peeled from the support.